Remy Maucherat wrote:
Hi,
I've been working on additions to CometEvent to implement the additional
Comet functionality that was agreed upon before creating the "trunk"
branch. Although not functional at the moment, I consider it to be
developed enough from an algorithmic standpoint to be proposed and
reviewed (it is also important to not continue an API fork for too long,
since otherwise it would be harder to merge, so some resolution is
needed). I went through a few revisions of the API, as more tweaks
appeared possible. The idea was to allow the extra functionality without
adding complexity or incompatible changes, since this is most likely
going to be an interim API.
The repository is at:
https://svn.apache.org/repos/asf/tomcat/sandbox/comet
I made a number of updates since this proposal (which has been vetoed)
was made. The API makes implicit a lot of behaviors which I found are
not needed for the end user, and attempts to be fairly high level. In
particular, I have rewritten the javadoc, which was self conflicting
(due to forgetting to update some wording inherited from TC 6.0). All
6.0.13 API usage should remain compatible (I do expect at least one
behavior fix in 6.0.x, though).
It has the following changes over the 6.0.x branch:
- additions of three methods in CometEvent (sleep and resume, and the
ready flag)
- sleep() delays request processing until either resume() is called, or a
timeout occurs
- sleep() also disables read events until resume() is called (in
addition to invoking a generic event, resume() also enables read events)
- resume() allows waking up requests which are "asleep" or waiting for
an IO event
- non blocking IO exclusively (with, as an exception to the rule, a
switch to blocking IO in very specific cases of synchronous IO operations)
- no additional data structures
- new ActionCode: ACTION_COMET_TIMEOUT (which is cleanup),
ACTION_COMET_RESUME (called by the resume() method),
ACTION_COMET_SLEEP (called by the sleep() method), ACTION_COMET_WRITE
(called by the CometEvent.ready() method without the need for an
explicit callback from the servlet - ready() knows the result of the
last write, and the servlet is supposed to not attempt any further
writing if ready() returns false)
- no additional features, like verification of caller threads (which I
consider useless)
- change to o.a.comet package
I hope I did not forget anything. Certain items could still be changed
(like the package name, or the name of the ready() method - the problem
with that one is that it does not particularly imply "writing", but OTOH
the old canWrite and isWriteable names were quite inelegant).
I don't want to block development forever, so if this proposal is
refused using an outright veto like the previous version of the
proposal, I will not block competing proposals using a veto of my own.
However, I will most likely stop participating in trunk development
(which is not the end of the world since I've been working on Tomcat for
pretty much forever, so it could be a good time to move on).
Comments ? / Votes ?
Rémy
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